Android example source code file (AbsSeekBar.java)

This example Android source code file (AbsSeekBar.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

absseekbar, android, attributeset, content, drawable, drawing, graphics, keyevent, no_alpha, override, paint, progressbar, rect, typedarray, ui

The AbsSeekBar.java Android example source code

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.widget;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.KeyEvent;
import android.view.MotionEvent;

public abstract class AbsSeekBar extends ProgressBar {
    private Drawable mThumb;
    private int mThumbOffset;
    
    /**
     * On touch, this offset plus the scaled value from the position of the
     * touch will form the progress value. Usually 0.
     */
    float mTouchProgressOffset;

    /**
     * Whether this is user seekable.
     */
    boolean mIsUserSeekable = true;

    /**
     * On key presses (right or left), the amount to increment/decrement the
     * progress.
     */
    private int mKeyProgressIncrement = 1;
    
    private static final int NO_ALPHA = 0xFF;
    private float mDisabledAlpha;
    
    public AbsSeekBar(Context context) {
        super(context);
    }

    public AbsSeekBar(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public AbsSeekBar(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        TypedArray a = context.obtainStyledAttributes(attrs,
                com.android.internal.R.styleable.SeekBar, defStyle, 0);
        Drawable thumb = a.getDrawable(com.android.internal.R.styleable.SeekBar_thumb);
        setThumb(thumb); // will guess mThumbOffset if thumb != null...
        // ...but allow layout to override this
        int thumbOffset = a.getDimensionPixelOffset(
                com.android.internal.R.styleable.SeekBar_thumbOffset, getThumbOffset());
        setThumbOffset(thumbOffset);
        a.recycle();

        a = context.obtainStyledAttributes(attrs,
                com.android.internal.R.styleable.Theme, 0, 0);
        mDisabledAlpha = a.getFloat(com.android.internal.R.styleable.Theme_disabledAlpha, 0.5f);
        a.recycle();
    }

    /**
     * Sets the thumb that will be drawn at the end of the progress meter within the SeekBar.
     * <p>
     * If the thumb is a valid drawable (i.e. not null), half its width will be
     * used as the new thumb offset (@see #setThumbOffset(int)).
     * 
     * @param thumb Drawable representing the thumb
     */
    public void setThumb(Drawable thumb) {
        if (thumb != null) {
            thumb.setCallback(this);

            // Assuming the thumb drawable is symmetric, set the thumb offset
            // such that the thumb will hang halfway off either edge of the
            // progress bar.
            mThumbOffset = thumb.getIntrinsicWidth() / 2;
        }
        mThumb = thumb;
        invalidate();
    }

    /**
     * @see #setThumbOffset(int)
     */
    public int getThumbOffset() {
        return mThumbOffset;
    }

    /**
     * Sets the thumb offset that allows the thumb to extend out of the range of
     * the track.
     * 
     * @param thumbOffset The offset amount in pixels.
     */
    public void setThumbOffset(int thumbOffset) {
        mThumbOffset = thumbOffset;
        invalidate();
    }

    /**
     * Sets the amount of progress changed via the arrow keys.
     * 
     * @param increment The amount to increment or decrement when the user
     *            presses the arrow keys.
     */
    public void setKeyProgressIncrement(int increment) {
        mKeyProgressIncrement = increment < 0 ? -increment : increment;
    }

    /**
     * Returns the amount of progress changed via the arrow keys.
     * <p>
     * By default, this will be a value that is derived from the max progress.
     * 
     * @return The amount to increment or decrement when the user presses the
     *         arrow keys. This will be positive.
     */
    public int getKeyProgressIncrement() {
        return mKeyProgressIncrement;
    }
    
    @Override
    public synchronized void setMax(int max) {
        super.setMax(max);

        if ((mKeyProgressIncrement == 0) || (getMax() / mKeyProgressIncrement > 20)) {
            // It will take the user too long to change this via keys, change it
            // to something more reasonable
            setKeyProgressIncrement(Math.max(1, Math.round((float) getMax() / 20)));
        }
    }

    @Override
    protected boolean verifyDrawable(Drawable who) {
        return who == mThumb || super.verifyDrawable(who);
    }

    @Override
    protected void drawableStateChanged() {
        super.drawableStateChanged();
        
        Drawable progressDrawable = getProgressDrawable();
        if (progressDrawable != null) {
            progressDrawable.setAlpha(isEnabled() ? NO_ALPHA : (int) (NO_ALPHA * mDisabledAlpha));
        }
        
        if (mThumb != null && mThumb.isStateful()) {
            int[] state = getDrawableState();
            mThumb.setState(state);
        }
    }
    
    @Override
    void onProgressRefresh(float scale, boolean fromUser) { 
        Drawable thumb = mThumb;
        if (thumb != null) {
            setThumbPos(getWidth(), thumb, scale, Integer.MIN_VALUE);
            /*
             * Since we draw translated, the drawable's bounds that it signals
             * for invalidation won't be the actual bounds we want invalidated,
             * so just invalidate this whole view.
             */
            invalidate();
        }
    }
    
    
    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        Drawable d = getCurrentDrawable();
        Drawable thumb = mThumb;
        int thumbHeight = thumb == null ? 0 : thumb.getIntrinsicHeight();
        // The max height does not incorporate padding, whereas the height
        // parameter does
        int trackHeight = Math.min(mMaxHeight, h - mPaddingTop - mPaddingBottom);
        
        int max = getMax();
        float scale = max > 0 ? (float) getProgress() / (float) max : 0;
        
        if (thumbHeight > trackHeight) {
            if (thumb != null) {
                setThumbPos(w, thumb, scale, 0);
            }
            int gapForCenteringTrack = (thumbHeight - trackHeight) / 2;
            if (d != null) {
                // Canvas will be translated by the padding, so 0,0 is where we start drawing
                d.setBounds(0, gapForCenteringTrack, 
                        w - mPaddingRight - mPaddingLeft, h - mPaddingBottom - gapForCenteringTrack
                        - mPaddingTop);
            }
        } else {
            if (d != null) {
                // Canvas will be translated by the padding, so 0,0 is where we start drawing
                d.setBounds(0, 0, w - mPaddingRight - mPaddingLeft, h - mPaddingBottom
                        - mPaddingTop);
            }
            int gap = (trackHeight - thumbHeight) / 2;
            if (thumb != null) {
                setThumbPos(w, thumb, scale, gap);
            }
        }
    }

    /**
     * @param gap If set to {@link Integer#MIN_VALUE}, this will be ignored and
     */
    private void setThumbPos(int w, Drawable thumb, float scale, int gap) {
        int available = w - mPaddingLeft - mPaddingRight;
        int thumbWidth = thumb.getIntrinsicWidth();
        int thumbHeight = thumb.getIntrinsicHeight();
        available -= thumbWidth;

        // The extra space for the thumb to move on the track
        available += mThumbOffset * 2;

        int thumbPos = (int) (scale * available);

        int topBound, bottomBound;
        if (gap == Integer.MIN_VALUE) {
            Rect oldBounds = thumb.getBounds();
            topBound = oldBounds.top;
            bottomBound = oldBounds.bottom;
        } else {
            topBound = gap;
            bottomBound = gap + thumbHeight;
        }
        
        // Canvas will be translated, so 0,0 is where we start drawing
        thumb.setBounds(thumbPos, topBound, thumbPos + thumbWidth, bottomBound);
    }
    
    @Override
    protected synchronized void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (mThumb != null) {
            canvas.save();
            // Translate the padding. For the x, we need to allow the thumb to
            // draw in its extra space
            canvas.translate(mPaddingLeft - mThumbOffset, mPaddingTop);
            mThumb.draw(canvas);
            canvas.restore();
        }
    }

    @Override
    protected synchronized void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        Drawable d = getCurrentDrawable();

        int thumbHeight = mThumb == null ? 0 : mThumb.getIntrinsicHeight();
        int dw = 0;
        int dh = 0;
        if (d != null) {
            dw = Math.max(mMinWidth, Math.min(mMaxWidth, d.getIntrinsicWidth()));
            dh = Math.max(mMinHeight, Math.min(mMaxHeight, d.getIntrinsicHeight()));
            dh = Math.max(thumbHeight, dh);
        }
        dw += mPaddingLeft + mPaddingRight;
        dh += mPaddingTop + mPaddingBottom;
        
        setMeasuredDimension(resolveSize(dw, widthMeasureSpec),
                resolveSize(dh, heightMeasureSpec));
    }
    
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (!mIsUserSeekable || !isEnabled()) {
            return false;
        }
        
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                setPressed(true);
                onStartTrackingTouch();
                trackTouchEvent(event);
                break;
                
            case MotionEvent.ACTION_MOVE:
                trackTouchEvent(event);
                attemptClaimDrag();
                break;
                
            case MotionEvent.ACTION_UP:
                trackTouchEvent(event);
                onStopTrackingTouch();
                setPressed(false);
                // ProgressBar doesn't know to repaint the thumb drawable
                // in its inactive state when the touch stops (because the
                // value has not apparently changed)
                invalidate();
                break;
                
            case MotionEvent.ACTION_CANCEL:
                onStopTrackingTouch();
                setPressed(false);
                invalidate(); // see above explanation
                break;
        }
        return true;
    }

    private void trackTouchEvent(MotionEvent event) {
        final int width = getWidth();
        final int available = width - mPaddingLeft - mPaddingRight;
        int x = (int)event.getX();
        float scale;
        float progress = 0;
        if (x < mPaddingLeft) {
            scale = 0.0f;
        } else if (x > width - mPaddingRight) {
            scale = 1.0f;
        } else {
            scale = (float)(x - mPaddingLeft) / (float)available;
            progress = mTouchProgressOffset;
        }
        
        final int max = getMax();
        progress += scale * max;
        
        setProgress((int) progress, true);
    }

    /**
     * Tries to claim the user's drag motion, and requests disallowing any
     * ancestors from stealing events in the drag.
     */
    private void attemptClaimDrag() {
        if (mParent != null) {
            mParent.requestDisallowInterceptTouchEvent(true);
        }
    }
    
    /**
     * This is called when the user has started touching this widget.
     */
    void onStartTrackingTouch() {
    }

    /**
     * This is called when the user either releases his touch or the touch is
     * canceled.
     */
    void onStopTrackingTouch() {
    }

    /**
     * Called when the user changes the seekbar's progress by using a key event.
     */
    void onKeyChange() {
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (isEnabled()) {
            int progress = getProgress();
            switch (keyCode) {
                case KeyEvent.KEYCODE_DPAD_LEFT:
                    if (progress <= 0) break;
                    setProgress(progress - mKeyProgressIncrement, true);
                    onKeyChange();
                    return true;
            
                case KeyEvent.KEYCODE_DPAD_RIGHT:
                    if (progress >= getMax()) break;
                    setProgress(progress + mKeyProgressIncrement, true);
                    onKeyChange();
                    return true;
            }
        }

        return super.onKeyDown(keyCode, event);
    }

}